The regulations will force more than 1,000 power plants and factories that withdraw at least 2 million gallons of water a day from adjacent waterways for cooling to take steps to minimize its toll on aquatic wildlife.

Marine animals, many of them juvenile, die by either being pinned or by being exposed to heat, chemicals and other stress after they are sucked inside the system. The EPA estimates 2.1 billion fish, crab and shrimp die annually.

"EPA is making it clear that if you have cooling water intakes you have to look at the impact on aquatic life in local waterways and take steps to minimize that impact," said Nancy Stoner, the EPA's acting assistant administrator for water, in a statement.

The rule is among a series issued by the Obama administration targeting various forms of air and water pollution from the nation's power plants, particularly coal-fired facilities. Coal-fired power plants already face limits on mercury and toxic air pollution, and will be the target of a new proposal due in June to regulate the gases blamed for global warming for the first time. The EPA is also working on new rules to deal with coal ash, the refuse left over from increasing air pollution controls, and discharges of metals and other toxics into waterways.

Republicans in Congress immediately painted the regulation as another attack on the nation's power producers. Sen. James Inhofe, R-Okla., vowed to work to get a vote to repeal it. However, any such effort is likely to be vetoed by the president.

"The EPA has released another rule that threatens the affordability and reliability of America's electricity, and I am committed to ensuring that Congress weighs in," Inhofe said.

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